1. Field of the Invention
The present invention relates to a reel-type slot machine, and more particularly to a slot machine which presents combined symbols visible on overlying concentric reels.
2. Description of the Related Art
Slot machines are grouped into two types, namely, a mechanical reel type in which reels are rotated, and a video type in which an electronic display is used to simulate the rotation of reels. In a slot machine of the video type, the rotation and stopping of mechanical reels are simulated by using graphical data and displayed on a display such as a CRT. Many players prefer the mechanical reel type because they suspect that the results of play have been intentionally controlled with the video type.
In a slot machine of the mechanical reel type, three reels for example are rotated at the same time, mechanically upon actuation of a start lever, or electrically with the help of motors, upon actuation of the start lever. The three reels are thereafter stopped sequentially by operating a stop button provided for each reel or by a stop signal randomly generated by a random timer. A win or hit is determined by a combination of symbols on the three stopped reels along a winning line viewed from the observation windows. If the symbol combination is a winning symbol combination, dividend coins are paid out or a special favor such as a bonus game is given to the player.
A drawback of conventional mechanical reel type slot machines is that the game is simple and monotonous because the conventional machines have all adopted the same method whereby a winning symbol combination is determined by a sequence of starting and stopping a single set of reels appearing in the observation windows. Moreover, the number of symbols on the outer circumference of each reel is limited by the outer diameter of the reel, it being impossible to increase the number of symbols above a certain limit. Therefore, the number of symbol combinations is limited, which reduces the interest in playing the game.